Actually the left hand side of Brewers Bay is probably as good as anywhere for a beginner. One of the most important things when snorkelling is to take it slowly. Far too many people splash, kick and seem to be in a race. If you do that, you won't see much at all. The water will hold you up, just move your legs slowly and gently and moreorless less float along and you will be a zed that you see far more than those rushing past you. Enjoy.